The company said the word is misspelled one out of every 10 times it is used because many other words with phonetically similar endings -- such as intercede and precede -- are spelled with the letter "c" instead of "s," The Daily Telegraph reported.
The researchers said they arrived at their conclusions by using a software program that went through thousands of documents available on the Internet, including published books, blogs and news articles.
Collins said other commonly misspelled words -- including conscience, indict, foreign, mortgage and phlegm -- are challenging because they their spelling is different from their phonetic pronunciations.
"The real spelling problems occur when people have (learned) the rules or have a bit of knowledge, but then make mistakes in how they apply this," said Ian Brookes, the managing editor of dictionaries at Collins.
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